1. Field of Invention
This invention relates to a conductive powder and a conductive material containing the same, and also relates to a method for producing a conductive powder.
2. Description of Related Art
The applicant had proposed a conductive powder for electroless plating that has protrusions of nickel or a nickel alloy on its surface (see Patent Document 1). The plating powder exhibits good conductivity due to the effects of the fine protrusions.
In addition to the technique, Patent Document 2 proposed a conductive particle having protrusions, which is obtained by adhering a nickel core material with a particle size of 50 nm to the surface of a core particle with a particle size of 4 μm and then conducting electroless plating of nickel. However, in the conductive particle obtained with this method, the adhesion between the core particle and the nickel core material is weak, and integrity is absent between the nickel film coated on the surface of the core particle and the protrusions. Hence, the protrusions are easily damaged when a pressure is applied to the conductive particle.
Another technique relating to conductive particles with protrusions is described in Patent Document 3. The conductive particle described in this document includes a base particle, and a Ni-containing conductive film that is formed on the surface of the base particle and has, on its surface, protrusions composed of aggregations of massive fine particles.
The applicant has further proposed a conductive powder that improves various performances as compared to the above conventional conductive powders (see Patent Document 4). The protrusions on the conductive particles in the conductive powder have a more slender shape as compared to the protrusions ever known before.